"As parents you look after your child, give them everything you can and try to set them up for a good life - and we can't do anything to help her," Mrs Archer says.

Finding out what was wrong with Katie was an emotionally charged process.

She had been having seizures for about a year and was developmentally lagging.

During hospital testing she was checked for pigmentation in her eyes, which can be an indicator of Batten's.

After a sleepless night, they were told her retinas were clear, and felt a huge sense of relief when they thought the worst-case scenario was ruled out. But a subsequent spinal tap, where the fluid was sent to Australia for testing, came back positive for Batten's disease at the end of August.

Mrs Archer says at least they are now dealing with a known quantity as horrific as the diagnosis is.

She says they know the path Katie's life will take.

What they don't know is the timeframe.

Four weeks ago she could run, now she is lucky if she can walk without falling over, Mr Archer says.

She can't communicate and gets frustrated at not being able to do small things like picking up a spoon.

One thing they can do is try to build memories while they can.

Plenty of family photos are being taken and they try to give Katie as many enjoyable experiences as possible.

Her grandad is giving her lots of tractor rides because it is one of the things she loves, along with the chance to go swimming and visit the zoo.

Katie is much-loved by siblings Caleb and Amy, who understand she is not going to get better.

Caleb was devastated at the news Katie wouldn't be joining him at Bayfield Primary School when she turned five.

The level of care Katie needs is all-consuming, so Mrs Archer has had to give up her part-time job. Mr Archer, who works from home, has had to give up other commitments like his role on the school's board of trustees.